Automated mechanical transmissions (AMTs) continue to increase their market penetration in vehicles used in commercial traffic such as the transport of heavy cargo loads. Such transmission systems generally comprise a multi-speed mechanical transmission having a mechanical transducer or actuator assembly, which receives signals from a controller or microprocessor and transmits corresponding mechanical commands to the shift and gear components of the transmission. The controller or microprocessor receives data from a plurality of sensors such as an operator controlled shift device, a throttle position sensor, an engine and various shaft speed sensors and other operating and vehicle parameter sensors and, according to various operating algorithms, calculations, lookup tables and the like, determines an appropriate transmission gear ratio and selects or maintains that gear ratio.
Determination of the appropriate gear ratio for a variety of vehicle operating conditions is important to the efficient operation of the vehicle. While the sophistication of AMT controllers continues to improve, some controllers on occasion incorrectly determine that a transmission gear ratio change is required. Transmission hunting, a cyclic repetition of gear shifts between adjacent gear ratios, is one example of such erroneous determinations by the AMT controller. In transmission hunting, a controller may erroneously determine that a shift to another gear ratio is required. Shortly after the shift is completed, the controller may then determine that a shift back to the previous gear ratio is required. Transmission hunting may occur when climbing a hill or grade. As a result of incorrect gear ratio change determinations, travelling comfort of the vehicle passengers may be reduced, and the fuel efficiency of the vehicle can decrease.